Hydrocarbon feedstocks intended for use in synthesis gas generation must first be desulphurised in order to protect sensitive downstream catalysts from deactivation. Sulphur removal is conventionally carried out using a combination of hydrodesulphurisation (HDS) catalysis (based typically on CoMo or NiMo catalysts) and zinc oxide based absorbents. In this process, the HDS catalyst converts any organosulphur species in the feed to hydrogen sulphide, which may be subsequently removed by reaction with ZnO. In order for the hydrodesulphurisation reaction to occur, it is necessary to have hydrogen present in the feed. As an alternative to the two-stage process discussed above, a single material that combines both hydrodesulphurisation activity and ability to absorb hydrogen sulphide can also be employed.
Nickel containing desulphurisation materials have been proposed previously for a variety of desulphurisation applications.
SU959821 discloses a catalyst for the desulphurisation of gases, comprising 0.6-5.0% wt nickel oxide, 5.4-10.0% wt copper oxide, 5-16% wt aluminium oxide and the remainder zinc oxide. The gases that may be desulphurised using this material were stated to be natural gases, gases produced during the refining and cracking of crude oil, and also process gases containing H2, CO and CO2. The catalysts were prepared by combining zinc oxide, copper oxide, basic nickel carbonate and aluminium oxide in an ammonium carbonate solution, and ageing the resultant mixture at temperatures in the range 45-85° C. The resultant mass was dried at 100-110° C. and calcined at 350-400° C.
EP1224970 discloses a catalyst for deep desulphurisation of a mineral oil corresponding to kerosene, comprising 5 to 25% by weight nickel oxide, 30 to 70% by weight zinc oxide, and aluminium oxide. The process for producing the deep desulphurisation catalyst comprised mixing a basic substance with each of an aqueous solution of a nickel salt and an aqueous solution of a zinc salt or with a mixed aqueous solution thereof to form precipitates separately or simultaneously, and mixing the precipitates with aluminium oxide or an aluminium oxide precursor, followed by shaping and calcining.
U.S. Pat. No. 6,274,533 discloses sorbent systems for the desulphurisation of cracked-gasoline or diesel fuels comprising a reduced bimetallic promoter formed of at least two metals selected from the group consisting of nickel, cobalt, iron, manganese, copper, zinc, molybdenum, tungsten, silver, tin, antimony and vanadium on a particulate support comprising zinc oxide. The preferred bimetallic promoter was a mixture of nickel and cobalt on a particulate support comprised of zinc oxide, silica and alumina. The methods disclosed for the preparation of these materials included addition of bimetallic promoter compounds to the support components prior to drying and calcining, or impregnation of dried and calcined support particulates with a solution that contains the elemental metals, metal oxides or metal-containing compounds of the selected promoter system. The preferred preparative route comprised the steps of: (a) admixing zinc oxide, silica and alumina so as to form a mixture in the form of a wet mix, dough, paste or slurry; (b) particulating the resulting mix to form granules, extrudates, tablets, pellets, spheres or microspheres; (c) drying the resulting particulate; (d) calcining the dried particulate; (e) impregnating the resulting calcined particulate with bimetallic promoter; (f) drying the impregnated particulate; (g) calcining the resulting dried particulate; and (h) reducing the calcined particulate product of (g) with a suitable reducing agent so as to produce a particulate composition having a substantially reduced bimetallic promoter content therein.